The drilling of various materials often generates chips which, unless conveyed away from the cutting features of the drill bit, can impede the drilling process. Certain materials, including composite materials such as carbon fiber reinforced plastic (CFRP), for example, are notorious for yielding large quantities of fine chips when drilled. Without effective removal of the chips thus generated, chip compaction often occurs, reducing the drill's ability to cut, increasing the generation of heat, and reducing the life of the drill. It is not uncommon for drill bits to be discarded after drilling only five holes or less in materials such as CFRPs.
Several arrangements for removing drill chips have been developed, including vacuum drilling systems, for example. In a typical vacuum drilling system, a generally hollow drill bit is employed having one or more openings located proximate to the cutting features of the drill bit, which openings are in communication with the hollow interior of the drill. A vacuum source is coupled to the hollow interior of the drill bit so that chips generated by the cutting features of the drill bit are drawn through the openings and through the hollow interior of the drill bit away from the cutting features of the drill. Examples of such arrangements are described in U.S. Pat. Nos. 3,032,129, 3,144,912, and 6,086,292.
In addition to requiring effective chip removal, many drilling applications also require precision. In such applications, the drill bit may be guided by a bushing or the like. In applications such as transfer drilling, the drill bit may be guided by a hole in a component for which a matching hole in a mating component is to be drilled. To maximize precision, the spacing between the drill bit and the guiding means (e.g., bushing or guide hole) should be minimized. This, however, leads to greater friction between the drill bit and the guiding means and thus to increased heat generation. Heat degrades the life of the drill and promotes chip compaction.
A need therefore exists for a drilling system that provides effective chip removal for problematic materials, such as CFRPs, while promoting drill bit longevity and precision.